Continuous in-line process for making ink-jet recording media comprising a radiation-cured coating layer

ABSTRACT

Ink-jet recording media and continuous in-line process for manufacturing such media are provided. The media can be printed with ink-jet printers to form images having good color density, brilliance, and resolution. The ink-jet recording media include a paper substrate coated on one surface with a radiation-curable composition and an ink-receptive composition. The back surface of the paper may be coated with a polymeric coating to reduce curl and improve dimensional stability. The media have a water vapor transmission rate of no greater than 12 grams/100 square inches/24 hours and preferably have a surface gloss of at least 70.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/863,552 having a filing date of May 23, 2001, which now has issued asU.S. Pat. No. 6,610,388 B2, the entire contents of which are herebyincorporated by reference.

BACKGROUND

1. Technical Field

This invention relates to imaging media suitable for use with ink-jetprinters. More particularly, the invention relates to ink-jet recordingmedia comprising a paper substrate coated on one surface with aradiation-curable composition and an ink-receptive composition. Theother surface of the paper may be coated with a polymeric coating toimprove the paper's dimensional stability. The invention alsoencompasses a continuous in-line process for making such imaging media.

2. Brief Description of the Related Art

Today, individual consumers and businesses are turning to ink-jetprinting systems and digital technology to produce many differentimaging media products. With the introduction of new computers,software, and digital cameras, consumers are now able to create greetingcards, posters, calendars, newsletters, fliers, window decals and thelike in the comfort of their own homes. Companies can create smallformat products such as business cards, company newsletters, brochures,promotional materials, overhead transparencies, and the like. Companiescan also create large indoor and outdoor advertising displays and othergraphic art materials for business presentations.

In an ink-jet printing process, liquid ink is squirted through very finenozzles in a printer. The resultant ink droplets form an image directlyon a recording medium that typically comprises a coated film or papersubstrate. The quality of the final image or text is partly dependent onthe composition of the ink-jet recording medium particularly thecoating(s) and substrate. The inks used in most ink-jet printers areaqueous-based inks containing molecular dyes or pigmented colorants.Water is the major component in aqueous-based inks. Small amounts ofwater-miscible solvents such as glycols and glycol ethers also may bepresent. Other ink-jet inks are non-aqueous based inks containingorganic vehicles (e.g., hydrocarbon solvents) as the major component.

“Photo-papers” are particularly popular, because a person can producephotographic-like images on these materials. Paper substrates, e.g.,plain papers, clay-coated papers, and polyethylene resin-coated papers,can be used to make photo papers. The paper substrate is coated withspecially formulated coatings that are capable of receivingaqueous-based inks from ink-jet printers.

Often, the substrate is a polyethylene-coated paper. Such papers canhave good dimensional stability and moisture resistance. Thepolyethylene coating acts as a moisture-barrier layer helping to preventthe aqueous ink vehicle from permeating into the base paper.Polyethylene-coated papers are commercially available from Jen-Coat,Inc. (Westfield, Mass.) and other companies under various trademarks.However, there are some disadvantages with using polyethylene-coatedpapers, including their manufacturing costs and thermal stability. Forexample, it may be difficult to use polyethylene-coated papers in hightemperature manufacturing operations, such as those where additionalcoating layers must be dried, because of polyethylene's thermoplasticproperties. Further, some polyethylene-coated papers tend to have lowsurface gloss which may be undesirable for some commercial applications.As an alternative, clay-coated papers can be used. The cost ofclay-coated papers is generally lower. But, clay-coated papers tend toabsorb the aqueous ink vehicle and this absorption may lead to curlingof the paper's edges and cockling of the paper's surface.

D'Anna et al., U.S. Pat. No. 5,800,884 discloses a gloss coatingcomposition comprising radiation curable oligomers and monomers, andphotosensitizers. The coating composition is applied to at least onesurface of a substrate and exposed to an ultraviolet light sourceresulting in curing of the composition onto the substrate's surface. Thepatent discloses that the coating can be applied to non-woven, woven,synthetic paper, paper, paperboard, plastic, or metal substrates. Thepatent further discloses that the coating composition can be used asprimer coat over a substrate's surface, wherein the coating surface iscapable of printing with ultraviolet or ultraviolet compatible inks.Alternatively, or in addition, to the primer coat, the coatingcompositions are used as a top coat over a substrate surface to impartgloss characteristics, good rub resistance, and flexibility to thesubstrate.

Nowak, U.S. Pat. No. 4,265,976 discloses an ultravioletradiation-curable coating composition comprising (1) chlorinated rubber,(2) chlorinated paraffin, (3) vinyl acetate, (4) trimethylolpropanetriacrylate, (5) photoinitiator, and (6) heat and light stabilizers forthe chlorocarbon components. The patent discloses that the coating hasutility as a moisture-barrier film for the protection of substrates suchas paper and cardboard. For example, the patent discloses the coatingsystem can provide a moisture-barrier coating on detergent boxes in asingle coat procedure.

Mehta et al., U.S. Pat. No. 5,219,641 discloses using aradiation-curable coating on certain substrates to make them receptiveto images from a thermal transfer printer. The coating is a blend ofradiation-curable oligomers and monomers, and optionally a free radicalinitiator. The patent discloses that the coating may be applied tocoated or non-coated electronic data processing papers, bond papers,high quality calendared papers, cast coated papers, and other businessforms.

The ink-jet industry is looking to develop new paper-based media capableof absorbing aqueous inks to form high quality images having good colordensity, brilliance, and resolution. The media should have goodmoisture-barrier properties and preferably have high surface gloss. Acost-effective and efficient manufacturing process for making such mediawould also be desirable. The present invention provides such ink-jetrecording media and a continuous in-line process for manufacturing themedia.

The ink-jet recording media of this invention comprise a radiation-curedlayer and polymeric ink-receptive layer. The radiation-cured layer helpsretain the surface gloss of the media and provides good moisture barrierproperties. Significantly, the radiation-cured layer is thermally stableat temperatures greater than temperatures at which conventionalpolyethylene and related thermoplastic materials (e.g., olefin-basedpolymers and copolymers) are thermally stable.

SUMMARY

The present invention relates to an ink-jet recording medium comprising:a) a paper substrate, b) a radiation-cured layer overlaying a surface ofthe paper substrate, and c) a polymeric ink-receptive layer overlayingthe radiation-cured layer, the ink-jet recording medium having a watervapor transmission rate of no greater than 12 grams per 100 squareinches per 24 hours (5 g/100 in²/24 hrs). Preferably, the water vaportransmission rate is no greater than 8 g/100 in²/24 hrs. The mediumpreferably has a glossy surface luster. In such glossy mediaembodiments, the surface gloss is at least 70, and it is more preferablyin the range of about 85 to about 95. In other embodiments, satin-likemedia having surface gloss values in the range of 20 to 70 can be made.In still other embodiments, matte-like media having surface gloss valuesless than 20 can be made.

Preferably, the paper substrate is a clay-coated paper having athickness in the range of about 4 to about 8 mils. The radiation-curedlayer can be formed by irradiating a coating comprising aradiation-curable oligomer and photoinitiator. Preferably, the coatingused to form the radiation-cured layer comprises at least about 60%oligomer and 3% photoinitiator by weight. The coating can furthercomprise radiation-curable monomer and additives. For example, a coatingcomprising 60% oligomer, 3% photoinitiator, 20% monomer, 15% pigment,and 2% UV light stabilizer by weight can be used. Suitable oligomersinclude acrylated polyethers, acrylated polyesters, and acrylatedacrylics. Suitable monomers include trimethylolpropane trimethacrylate.Suitable photoinitiators include 1-hydroxy-cyclohexyl phenyl ketone anda blend of trimethylbenzophenone, polymeric hydroxy ketone, andtrimethylbenzoyldiphenyl phosphine oxide. Generally, the radiation-curedlayer has a weight in the range of about 1 to about 40 grams/squaremeter. Ultraviolet light or electron beam irradiation can be used tocure the coating.

The ink-receptive layer can comprise a water-soluble binder resin, forexample, polyvinyl alcohols, poly(vinyl pyrrolidone),poly(2-ethyl-2-oxazoline), methylcellulose, poly(ethylene oxide), andcopolymers and mixtures thereof. Preferably, the coating comprises atleast 40% water-soluble binder by weight. The coating can furthercomprise a water-dispersible resin. Multiple ink-receptive layers can beapplied to substrate. Generally, the dry coat weight of theink-receptive layer is in the range of about 5 to about 50 grams/squaremeter.

In another embodiment of this invention, the back surface of the basepaper is coated with a polymeric coating that further helps preventmoisture from penetrating into the base paper. Suitablewater-dispersible resins include, for example, polyvinyl chloride; vinylchloride copolymers; polyvinylidene chloride; vinylidene chloridecopolymers; acrylates; methacrylates; polyvinyl acetate;polyacrylonitrile; polystyrene; styrene copolymers; and mixturesthereof. Alternatively, the polymeric layer on the back surface of thepaper can be a radiation-cured layer formed by irradiating a coatingcontaining radiation-curable oligomers, monomers, photoinitiators andadditives.

The present invention also relates to a continuous in-line process formaking an ink-jet recording medium. In one embodiment, the processcomprises the steps of a) applying a radiation-curable coating to asurface of a substrate material, b) irradiating the radiation-curablecoating so that the coating undergoes a curing process, and c) applyingan ink-receptive coating over the irradiated coating. Preferably, themedia produced by the continuous process have a water vapor transmissionrate of no greater than 12 g/100 in²/24 hrs and more preferably nogreater than 5 g/100 in²/24 hrs. Glossy media having a surface glossgreater than 70 as well as satin-like media having a surface gloss inthe range of 20 to 70 and matte-like media having a surface gloss lessthan 20 can be made. The irradiated coating can be treated with coronadischarge prior to applying the ink-receptive coating. In anotherembodiment, a coating comprising adhesion promoters can be applied overthe irradiated coating prior to application of the ink-receptivecoating. As described above, the back surface of the substrate materialcan be coated with a polymeric coating to enhance the material'sdimensional stability. The continuous in-line process can run at a speedof at least about 60 feet per minute. The irradiated coating has goodthermal stability. Thus, the substrate comprising the irradiated coatingcan be subjected to further treatments and processing at temperatures(e.g., 140° C. to 200° C.) greater than temperatures at whichconventional polyethylene and related thermoplastic materials (e.g.,olefin-based polymers and copolymers) are typically treated andprocessed.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 is a schematic side view of one embodiment of the ink-jetrecording medium of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the ink-jet recording medium comprises a papersubstrate (10) having two surfaces. The first surface which is coatedwith the radiation-cured layer and ink-receptive layer may be referredto as the “front” or “imaging” surface. The second surface which isopposite to the first surface may be coated with the polymeric coatingand may be referred to as the “back” or “non-imaging” surface. Papersubstrates are known in the ink-jet industry, and any suitable paper maybe used in the present invention. For example, plain papers, clay-coatedpapers, or resin-coated papers may be used. Preferably, the paper is aclay-coated paper. Suitable paper substrates include, for example,Centura Cover 60# paper (available from Consolidated Papers, Inc.) andPolyjet Base 112# paper (available from P.H. Glatfelter Company). Thebase weight of the paper is not particularly restricted, but it shouldbe generally in the range of about 80 grams per square meter (gsm) toabout 250 gsm, preferably in the range of 130 gsm to 180 gsm. Thethickness of the paper is not particularly restricted, but it should begenerally in the range of about 4 mils to about 8 mils. The papersubstrate may be pre-treated with conventional adhesion promoters toenhance adhesion of the coatings to the paper or other primer coating.

As shown in FIG. 1, a radiation-cured layer (12) overlays the frontsurface of the base paper. The radiation-cured layer is prepared byfirst applying a radiation-curable coating to the paper substrate. Thecoating comprises radiation-curable oligomers and monomers such asacrylated oligomers, multifunctional acrylate monomers, difunctional andmonofunctional monomers, and mixtures thereof. Radiation from anelectron beam or ultraviolet (UV) light source is used to cure the wetcoating. The radiation induces the formation of free radicals thatinitiate polymerization of the oligomers and monomers. In electron beamradiation, a barrage of electrons initiates the free radicalpolymerization. In ultraviolet (UV) light radiation, photoinitiators(photosensitizers) absorb the UV light and initiate the free radicalpolymerization.

Generally, the radiation-curable oligomers and monomers are commerciallyavailable. For example, acrylated oligomers such as acrylatedpolyethers, acrylated polyesters, and acrylated acrylics may be used. Itis preferred that a relatively hydrophobic oligomer be used in theradiation-curable coating. Such a compound helps provide theradiation-cured layer with good moisture barrier properties because asthe hydrophobicity of the oligomer increases, the moisture barrierproperties improve. As a result, moisture is less likely to permeateinto the base paper and paper cockling and curl are minimized. Suitableacrylated oligomers that are commercially available include LAROMER PE44F (acrylated polyester) and LAROMER 8981 (acrylated polyester)available from BASF Corp.; EBECRYL 588 (chlorinated acrylated polyester)available from UCB Chemicals Corp.; and CN 301 (polybutadienedimethacrylate) and CN 302 (polybutadiene diacrylate) available fromSartomer Co. Preferably, the radiation-curable coating comprises anoligomer in an amount of at least about 60% based on weight of thecoating formulation. More preferably, the coating comprises aradiation-curable oligomer selected from the group consisting ofacrylated polyesters, polybutadiene dimethacrylate, and polybutadienediacrylate.

Suitable radiation-curable monomers include multifunctional acrylatessuch as pentaerythritol triacrylate (PETA), trimethylolpropanetriacrylate (TMPTA), 1,6 hexanediol diacrylate (HODA), tritripropyleneglycol diacrylate (TRPGDA), and triethylene glycol diacrylate (TREGDA).Examples of monomers that are commercially available include TMPTA-N(trimethylolpropane triacrylate) and EB-40 (tetraacrylate monomer)available from UCB Chemicals Corp. Difunctional and monofunctionalmonomers also may be used. Examples of monofunctional monomers include2-ethylhexyl acrylate, vinyl acetate, butyl acrylate, dimethylaminoethylacrylate, isobutoxymethyl acrylamide, and dimethylacrylamide.Preferably, the radiation-curable coating comprises a monomer in anamount of about 20% based on weight of the coating formulation. Morepreferably, the radiation-curable monomer is trimethylolpropanetriacrylate (TMPTA).

In the present invention, UV light radiation is preferably used to curethe coating, and the coating formulation comprises a photoinitiator. Asdiscussed above, in UV light radiation, photoinitiators in the coatingabsorb the UV light and initiate free radical polymerization. Examplesof suitable photoinitiators include Benzoin ethers (Norrish type Iinitiator) and Benzophenone (Norrish type II initiators that requireamine coinitiators to be active). IGRACURE 184 (1-hydroxy-cyclohexylphenyl ketone) and phenylbis (2,4,6-trimethyl benzoyl)-phosphine oxideare available from Ciba Specialty Chemicals Corp., and ESACURE KTO-46(blend of trimethylbenzophenone, polymeric hydroxy ketone, andtrimethylbenzoyldiphenyl phosphine oxide) is available from Sartomer Co.Preferably, the radiation-curable coating comprises a photoinitiator inan amount of at least about 3% based on weight of the coatingformulation. More preferably, the coating comprises a photoinitiatorselected from the group consisting of 1-hydroxy-cyclohexyl phenyl ketoneand a blend of trimethylbenzophenone, polymeric hydroxy ketone, andtrimethylbenzoyldiphenyl phosphine oxide.

For purposes of the present invention, it is important that the ink-jetrecording media have a water vapor transmission rate of no greater than12.0 grams/100 square inches/24 hours as measured per the Test Methodsdescribed below. Preferably, the water vapor transmission rate is nogreater than 5.0 g/100 in²/24 hrs. With such media, the ink-receptivelayer can absorb aqueous-based inks, and the inks tend not to permeateinto the base paper. Thus, paper curling, cockling, and other printingdefects can be minimized. It has been found that not allradiation-curable compositions are suitable for use in this invention.As shown in the following comparative examples, some radiation-curablecoatings do not impart sufficient moisture barrier properties to themedium.

The thermal stability of the radiation-cured layer is also an importantproperty. As discussed above, the substrate comprising the irradiatedcoating can be subjected to further treatments and processing attemperatures (e.g., 140° C. to 200° C.) greater than temperatures atwhich conventional polyethylene and related thermoplastic materials(e.g., olefin-based polymers and copolymers) are thermally stable.Ink-receptive inter-coats and topcoats can be applied to theradiation-cured layer, and these coatings can be subsequently processedwithout distorting or damaging the radiation-cured layer. The thermalstability of the radiation-cured can provide significant processingadvantages.

For example, the thermal stability of the radiation-cured layer canpermit fast or more complete drying of subsequent coating layers.Second, this thermal stability can provide for important chemicalreactions to occur during processing of the media, e.g. a useful degreeof cross-linking in the ink-receptive layer. Cross-linking in theink-receptive layer may be important in achieving good water fastness asdemonstrated in the Examples below. Third, this thermal stability canallow subsequent coating layers to be physically manipulated withrespect to each other and external objects. In particular, the thermalstability of the radiation-cured layer makes it possible to melt thecoating layers to achieve interlayer adhesion, external object adhesione.g., with a laminating film, or a desired surface texture in differentregions of the medium.

In addition, the radiation-curable coating may comprise additives suchas, for example, inhibitors, surfactants, waxes, cure accelerators,defoaming agents, pigments, dispersing agents, optical brighteners, UVlight stabilizers (blockers), UV absorbers, adhesion promoters, and thelike. Inhibitors are used to retard or stop undesirable polymerizationof the oligomers and monomers. The addition of such inhibitors to thecoating formulation may be beneficial if the formulation will be placedin storage for an extended period of time. If desired, white pigmentsmay be added to modify the whiteness of the paper. Preferably, theradiation-curable coating comprises pigment in an amount of about 15% byweight and an UV light stabilizer in an amount of about 2% based onweight of the coating formulation.

In practice, the radiation-curable oligomers and monomers are blendedtogether with a photoinitiator and additives. The mixture may be heatedto reduce its viscosity. The coating formulation may be applied to thebase paper by a conventional method to form a uniform coating. Suitablemethods for coating the base paper include, for example, Meyer-rod,roller, blade, wire bar, dip, solution extrusion, air-knife, curtain,slide, doctor-knife, and gravure methods. UV light may be used to curethe wet coating. Generally, the UV light has a wavelength in the rangeof about 200 nm to about 400 nm. Commercial UV light curing equipmentmay be used. Generally, such equipment includes an UV light source(e.g., a tubular glass lamp), reflectors to focus or diffuse the UVlight, and a cooling system to remove heat from the lamp area. Aftercuring, the paper may be treated with corona discharge to improve itsadhesion to the ink-receptive layer. Generally, the weight of theradiation-cured layer is in the range of about 1 to about 40 grams persquare meter (gsm), and the preferable weight is about 4 to about 15gsm.

The paper substrate is coated with a polymeric ink-receptive layer (14)that overlays the radiation-cured layer. The ink-receptive layer iscapable of absorbing aqueous-based inks to form glossy images havinggood color gamut and optical density.

The polymeric ink-receptive layer can be prepared from a coatingformulation comprising at least one water-soluble binder resin. Suitablewater-soluble binder resins include, for example, those selected fromthe group consisting of polyvinyl alcohols; modified polyvinyl alcohols(e.g., carboxyl-modified PVA, sulfonic-modified PVA, acrylamide-modifiedPVA, cationic-modified PVA, long chain alkyl-modified-PVA,silicone-modified PVA, maleic acid-modified PVA, and itaconicacid-modified PVA); poly(vinyl pyrrolidone); vinyl pyrrolidonecopolymers; poly(2-ethyl-2-oxazoline); poly(ethylene oxide);poly(ethylene glycol); poly(acrylic acids); starch; modified starch(e.g., oxidized starch, cationic starch, hydroxypropyl starch, andhydroxyethyl starch), cellulose; cellulose derivatives (e.g., oxidizedcellulose, cellulose ethers, cellulose esters, methyl cellulose,hydroxyethyl cellulose, carboxymethyl-cellulose, benzyl cellulose,phenyl cellulose, hydroxypropyl cellulose, ethyl hydroxyethyl cellulose,hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxybutylmethyl cellulose, dihydroxypropyl cellulose, hydroxypropylhydroxyethyl cellulose, chlorodeoxycellulose, aminodeoxycellulose,diethylammonium chloride hydroxyethyl cellulose, hydroxypropyl trimethylammonium chloride hydroxyethyl cellulose, sodium cellulose sulfate, andsodium carboxymethylhydroxyethyl cellulose); alginates and water-solublegums; dextrans; carrageenan; xanthan; chitin; proteins; gelatins; agar;and mixtures thereof.

Preferably, the ink-receptive layer comprises at least one water-solublebinder resin in an amount of at least 40% and more preferably in anamount of 45 to 96% by weight based on dry weight of the ink-receptivelayer. More preferably, the water-soluble binder resin is selected fromthe group consisting of polyvinyl alcohols; poly(vinyl pyrrolidone);poly(2-ethyl-2-oxazoline); methylcellulose; poly(ethylene oxide); andcopolymers and mixtures thereof.

In addition, the ink-receptive coating formulation may also contain awater-dispersible resin. Suitable water-dispersible resins include, forexample, those selected from the group consisting of polyvinyl chloride;vinyl chloride copolymers (e.g., ethylene-vinyl chloride);polyvinylidene chloride; vinylidene chloride copolymers; acrylates;methacrylates; polyvinyl acetate; vinyl acetate copolymers (e.g.,ethylene-vinyl acetate copolymers, and acrylic-vinyl acetatecopolymers,) polyacrylonitrile; polystyrene; styrene copolymers (e.g.,styrene-maleic acid anhydride copolymers and styrene-butadienecopolymers); rubber latex; polyesters; vinyl-acrylic terpolymers,polyacrylonitrile; acrylonitrile copolymers (e.g.,butadiene-acrylonitrile copolymers, butadiene-acrylonitrile-styreneterpolymers); polyurethanes; and mixtures thereof.

In accordance with the present invention, ink-jet recording media havingdifferent surface finishes can be made. Preferably, the medium has ahigh surface gloss (greater than 70), and more preferably the surfacegloss is in the range of about 85 to about 95. Such media are capable ofabsorbing aqueous-based inks to form glossy images having good colorgamut and optical density. Conventional ink-jet printers, e.g., an EncadNovajet Pro50, Océ Printing Systems' Océ CS 5070, Hewlett-Packard HP2500 or HP970 Cse can be used to print such images. The imaged ink-jetrecording media can be used to make laminates by laminating atransparent film over the printed image. Both cold laminates (i.e.,films that are laminated at room temperature), and hot laminates (i.e.,films that are laminated at elevated temperatures) can be produced.

In other embodiments, satin-like media having surface gloss values inthe range of 20 to 70 may be made. In still other embodiments,matte-like media having surface gloss values less than 20, e.g., in therange of 1 to 20, may be made.

Primarily, the ink-receptive layer imparts surface luster to the media,but the radiation-cured layer is also significant, because it helpsretain surface luster.

The ink-receptive coating may also contain cationically-modifiedpolymers that act as dye fixatives, e.g., polyquaternary ammonium salts.Further, the ink-receptive coating may contain additives such aspigments. White pigments such as titanium dioxide, zirconium oxide, zincoxide, zinc sulfide, antimony oxide, barium sulfate, and calciumcarbonate may be added to modify the whiteness of the paper. Otherpigments, such as silica, alumina, alumina hydrate, clays, glass,polystyrene, starch, poly(methyl methacrylate), polytetrafluoroethylene,and the like may be added to improve the coating's ink absorptioncapabilities and modify its surface friction. In addition, surfaceactive agents that control the wetting or spreading action of thecoating, anti-static agents, suspending agents, acidic compounds tocontrol the pH of the coating, optical brighteners, UV lightstabilizers, defoaming agents, waxes, plasticizers, and the like may beadded to the formulation.

In the present invention, the paper substrate may be coated withmultiple ink-receptive layers. For example, a coating formulation (i.e.,inter-coat or prime coat) comprising water, poly(vinyl pyrrolidone),poly(vinyl alcohol), polyurethane, and an optical brightener may beapplied over the radiation-cured layer to form a first ink-receptivelayer. After the inter-coat has been dried, a second coating formulation(i.e., top coat) comprising water, methyl cellulose, polyethylene oxide,polyurethane, and alumina may be applied over the first ink-receptivelayer to form a second ink-receptive layer.

Further, the media may comprise an intermediate coating layer(s) betweenthe radiation-cured and ink-receptive coating layers. For example, acoating comprising adhesion promoters may be applied over theradiation-cured layer to enhance adhesion of the radiation-cured layerto the ink-receptive layer.

In practice, a water-soluble binder resin may be blended with water, anda water-dispersible binder resin (optional) and additives (optional) toform a coating formulation. A pre-mix containing a portion of thewater-soluble resins may be prepared first in a small vessel and thenadded to a larger vessel. Subsequently, additives and other resins maybe added and mixed together in the larger vessel. Various coatingmethods may be used to apply the ink-receptive coating to the substrateincluding Meyer-rod, roller, blade, wire bar, dip, solution extrusion,air-knife, curtain, slide, doctor-knife, and gravure methods. Thecoating formulations should have a low and consistent viscosity so thatthey can be coated easily onto the radiation-cure layer. The coatedpaper may be placed in a forced hot air oven to dry the ink-receptivelayer. Generally, the dry coat weight of the ink-receptive layer is inthe range of about 5 to about 50 gsm, and the preferable weight is about15 to about 25 gsm.

In addition, the back surface of the base paper may be coated apolymeric coating (16) that further helps prevent moisture frompenetrating into the base paper. The polymeric coating on the backsurface of the paper enhances the paper's dimensional stability andhelps minimize paper curling, cockling, and other defects.

In one embodiment, a polymeric coating (16) comprising awater-dispersible film-forming resin may be prepared. Suitablewater-dispersible resins include, for example, polyvinyl chloride; vinylchloride copolymers (e.g., ethylene-vinyl chloride); polyvinylidenechloride; vinylidene chloride copolymers; vinyl acrylic copolymers,vinyl acrylic terpolymers, polyacrylates; polymethacrylates; polyvinylacetate; polyacrylonitrile; polystyrene; styrene butadiene copolymers,styrene copolymers; and mixtures thereof. An aqueous coating formulationcontaining the film-forming resin may be prepared and applied to theback surface of the base paper using the coating methods describedabove. The polymeric coating may contain the above-described additivesparticularly waxes and pigments. In other embodiments, the polymericlayer on the back surface of the paper is a radiation-cured layerprepared from a coating containing radiation-curable oligomers,monomers, photoinitiators and additives as described above. If apolymeric coating is applied to the back surface, the dry coat weight ofthe polymeric layer is generally in the range of about 5 to about 40gsm, and the preferable weight is about 15 to about 25 gsm.

The present invention also encompasses a continuous, in-line process formaking an ink-jet recording medium. In general, the process comprisesthe steps of: a) applying a radiation-curable coating to a surface of asubstrate material, b) irradiating the radiation-curable coating so thatthe coating undergoes a curing process, and c) applying an ink-receptivecoating over the irradiated coating.

While not wishing to be bound by any theory, it is believed that thecontinuous, in-line process of this invention may provide advantagesover other production methods. As discussed above, the substrate iscoated with a radiation-curable composition, and the coating isirradiated soon thereafter. The irradiated coating undergoes a curingprocess comprising multiple constituent chemical and physical processes.The constituent irradiation and curing processes include the formationof active sites by irradiation (typically free radicals), the reactionor deactivation of these sites (typically through cross-linking orquenching with adventitious oxygen), the thermally and mechanicallyinduced relaxation of the coating morphology to more stableconfigurations (typically the molecular relaxation to configurationsthat are more stable under the circumstances), drying, and similarprocesses.

It is believed that the irradiated coating, as it undergoes the curingprocess, will respond to post in-line treatments differently than eithera fully cured or a non-irradiated coating (e.g., the above-describedpolyethylene-coated papers). The “freshly irradiated” coating will havesurface properties that are different than those of a substrate having afully cured or a non-irradiated coating. These differences can beexploited to make subsequently applied coating layers adhere eitherstrongly or weakly to the freshly irradiated coating. Further, thesurface properties of the “freshly irradiated coating” can be exploitedto increase production efficiency, reduce power consumption, or alterthe composition of subsequently applied coating layers. For example, thefreshly irradiated coating can be corona-treated as the substratetravels along the production line. If a coating layer must be subjectedto corona treatment for a specific period of time in order to produce alayer having acceptable surface properties, it is possible that the sameproperties could be imparted to a “freshly irradiated” coating in lesstime using the same corona treatment. As a result, the production linecould be run at higher speeds, or power delivered to the coronadischarge unit could be reduced, or space requirements for the coronatreatment station could be reduced.

The in-line irradiation of the radiation-curable coating can provideadditional advantages. An important advantage relates to chemicalinteractions between the “freshly irradiated” coating and posttreatments. Some of the most reactive chemical units present uponirradiation, such as free radicals, are not present to a useful degreein a fully cured coating. A coating designer can employ a “freshlyirradiated” coating to impart desirable properties to the ink-jetrecording media. Also, the physical, or material, properties of a“freshly irradiated” coating and a fully cured coating are different.Typically, the “freshly irradiated” coating is softer and more compliantthan a fully cured one. As a result, the freshly irradiated coating canbe processed advantageously using physical adhesion, pattern impression,and similar processes. Further, since the “freshly irradiated” coatingis not fully cured, molecular motion and transport into and out of thecoating tends to be easier. This molecular motion and transport mayallow for interfacial blending with other coating layers, and this canbe advantageous in improving adhesion, controlling curl of the media,and responding to other external environmental factors such as changesin humidity.

It may be advantageous to treat the irradiated coating within one (1)minute of irradiation. In such a process, the irradiation station andnext treatment station (e.g., a corona discharge unit) in the productionline would be within sixty (60) feet of each other. The substrate wouldtravel at a speed of at least sixty (60) feet per minute as itprogressed along the production line.

The invention is further illustrated by the following examples using thebelow Test Methods, but these examples should not be construed aslimiting the scope of the invention.

Test Methods

Water Vapor Transmission (WVT)

The water vapor transmission (WVT) rate of the samples was measuredusing a Vapometer (available from Thwing-Albert Instrument Company)according to the standard procedures described in the instrument manualprovided by the manufacturer. Particularly, the samples wereequilibrated at 15° C. and 20% relative humidity for about 24 hours. Thewater vapor transmission (WVT) was then measured on a Vapometer at 15°C. and 20% relative humidity for 24 hours. Measurements were made onthree (3) samples, and the average value was reported.

Surface Gloss

The surface gloss of the samples was measured using a Micro Tri-GlossMeter (available from BYK Gardner, Inc.) according to the standardprocedures described in the instrument manual provided by themanufacturer. Particularly, the sample was cut into sheets measuring 8.5inch by 11 inch. The surface gloss was measured on the sheets prior toimaging (printing). The Micro-Tri Gloss Meter was calibrated at sixty(60) degrees using the standard supplied by the unit. The sample wasplaced on a flat surface and the surface gloss was measured at sixty(60) degrees. Measurements were made on three (3) samples, and theaverage value was reported.

Color Gamut

The media samples were imaged (printed) with an Encad Novajet Pro50printer containing GS ink using an IAS2 test pattern. The printedsamples were stored at room temperature for 24 hours. Subsequently, thecolor gamut of each sample was measured with a X-RITE 918 TristimulusReflection Colorimeter (available from X-Rite, Inc.) using standardprocedures described in the instrument manual provided by themanufacturer. Generally, media having higher color gamut values provideimages of higher color quality.

Optical Density

The media samples were imaged (printed) with a multicolored test patternusing an Encad Novajet Pro50 printer containing GS ink. The printedsamples were stored at room temperature for 24 hours. Subsequently, theoptical density of black ink for each sample was measured with a X-Rite408 Reflection Densitometer (available from X-Rite, Inc.) using standardprocedures described in the instrument manual provided by themanufacturer. Generally, media having higher optical density valuesprovide images of higher quality and resolution.

Thermal Stability

The thermal stability of the radiation-cured layer on paper substratesamples was tested. The test was carried out at set temperatures in therange of 150° C. to 200° C., but it can be carried out at any desiredtemperature. The paper substrate samples were coated with aradiation-curable coating, and the coating was irradiated as describedin the Examples below. The irradiated, coated surface of the papersubstrate was placed in contact with a heated plate for one (1) minute.Then, the coated surface of the paper was visually inspected todetermine whether or not there was any damage or changes to the surface.Such changes could be a chemical change or a significant physical changesuch as melting or other structural modification. If no surface damageor change was observed, then the coated surface was rated as a “Pass”for that test temperature. If surface damage or change was observed,then the coated surface was rated as a “Fail” for that test temperature.

Water-Fastness

The media samples were imaged (printed) using a small format ink-jetprinter, Hewlett-Packard 970 Cxi. The printed samples were stored atroom temperature for 24 hours. The density of each of the colored printareas on each sample was measured with a X-Rite 408 ReflectionDensitometer (available from X-Rite, Inc.) using standard proceduresdescribed in the instrument manual provided by the manufacturer.

The printed samples were then immersed in water for 12 hours. The wet,printed samples were removed and dried at room temperature for 12 hours.Then, the density of each of the colored print areas on each sample wasmeasured with an X-Rite 408 Reflection Densitometer. The loss percentage(%) of color was calculated according to the following equation:${\frac{\left( {{Initial}\quad{Density}} \right) - \left( {{Final}\quad{Density}} \right)}{\left( {{Initial}\quad{Density}} \right)} \times 100} = {{loss}\quad\%\quad{of}\quad{color}}$

Generally, media having a relatively high percentage of color losspossess poor water-fastness, and media having a relatively lowpercentage of color loss possess good water-fastness.

WORKING EXAMPLES

In the following examples, percentages are by weight based on weight ofthe coating formulation, unless otherwise indicated. The resultingink-jet recording media samples were evaluated, and the results are setforth in Tables 1 and 2 below.

Example 1

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F¹ 95 wt. % Irgacure184² 5 wt. % Ink-Receptive Coating (Intercoat) Water 70.5 wt. % PVA KM118³ 4 wt. % PVP K-60⁴ 16 wt. % Witcobond 213⁵ 9 wt. % BYK-380⁶ 0.5 wt.% Ink-Receptive Coating (Topcoat) Water 90.6 wt. % PVA KM 118 4 wt. %PVP K-60 5 wt. % BYK-380 0.3 wt. % Citric Acid 0.1 wt. % PolymericCoating for Back Surface (Aqueous) Vancryl 610⁷ 93.7 wt. % Lanco PEW1555⁸ 5 wt. % Surfynol SE-F⁹ 1.0 wt. % Surfynol CT 171¹⁰ 0.2 wt. % DREWPlus L-407¹¹ 0.1 wt. % ¹Polyester acrylate (Oligomer), available fromBASF Corp., Charlotte, NC 28273. ²1-Hydroxycyclohexyl phenyl ketone(photoinitiator), available from Ciba Specialty Chemicals Corp.,Tarrytown, NY 10591. ³Polyvinyl alcohol, available from Kuraray Company,LTD. ⁴Polyvinyl pyrrolidone, available from ISP Technologies Inc.,Wayne, NJ 07470. ⁵Polyurethane dispersion, available from CromptonCorp., Greenwich, CT 06831. ⁶An acrylic leveling additive, availablefrom BYK-Chemie USA, Wallingford, CT 06492. ⁷Ethylene-vinyl chloridecopolymer emulsion, available from Air Products, Allentown, PA 18195.⁸Low molecular weight polyethylene wax, available from Lubrizol,Wickliffe, OH 44092. ⁹Ethoxylated 2,4,7,9-Tetramethyl 5 Decyn-4,7-Diol,available from Air Products, Allentown, PA 18195. ¹⁰A dispersant agent,available from Air Products, Allentown, PA 18195. ¹¹Modifiedpolysiloxane copolymer, available from Drew Industrial Division,Boonton, NJ 07005.

The radiation-curable coating was applied to the front surface of a 5.5mil clay-coated paper substrate (Centura Cover 60# paper available fromConsolidated Papers Inc.) using an offset gravure coater with a gravureroll (85 pyramid roll). The wet coating was cured by a Fusion UV lightcuring system (Model VP6/I600) (available from Fusion UV Systems, Inc.,Gaithersburg, Md. 20878) with two rows of 300 watts/cm H-bulbs. The UVlamp power intensity was set at 100%. After UV curing, theradiation-cured layer was subjected to corona discharge treatment.

After corona discharge treatment, the first ink-receptive coating(intercoat) was applied over the radiation-cured layer using a Meyerrod, and the coating was dried at 225° F. The first ink-receptive layercomprised 28% polyvinyl alcohol, 51% polyvinyl pyrrolidone, 19%polyurethane, and 2% acrylic leveling agent by weight based on dryweight of the ink-receptive layer. The second ink-receptive coating(topcoat) was applied over the intercoat using a Meyer rod and dried at225° F. The second ink-receptive layer comprised 62% polyvinyl alcohol,34% polyvinyl pyrrolidone, 2.4% acrylic leveling agent, and 2.5% citricacid by weight based on dry weight of the ink-receptive layer.

The polymeric coating was applied to the back surface of the paper usinga Meyer rod, and the coating was dried at 220° F. The polymeric coatingcomprised about 88% ethylene-vinyl chloride copolymer, 9% low molecularweight polyethylene wax, 2.8% diol surfactants, and 0.2% modifiedpolysiloxane copolymer by weight based on dry weight of the polymericcoating.

Example 2

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F 75 wt. % TMPTA-N¹ 20wt. % Irgacure 184  5 wt. % Ink-Receptive Coating (Intercoat) Samecomposition as described in Example 1. Ink-Receptive Coating (Topcoat)Same composition as described in Example 1. Polymeric Coating for BackSurface (Aqueous) Same composition as described in Example 1.¹Trimethylolpropane triacrylate (tri-functional monomer), available fromUCB Chemicals Corp., Smyrna, GA 30080.

In this Example 2, the radiation-curable coating contained aradiation-curable monomer (TMPTA-N) along with an oligomer andphotoinitiator. The ink-receptive and moisture-barrier coatings had thesame compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

EXAMPLE 3

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F 38 wt. % Ebecryl 588¹38 wt. % TMPTA-N 20 wt. % Irgacure 184  4 wt. % Ink-Receptive Coating(Intercoat) Same composition as described in Example 1. Ink-ReceptiveCoating (Topcoat) Same composition as described in Example 1. PolymericCoating for Back Surface (Aqueous) Same composition as described inExample 1. ¹Chlorinated polyester acrylate, UCB Chemicals Corp., Smyrna,GA 30080.

In this Example 3, the radiation-curable coating contained tworadiation-curable oligomers (Laromer PE 44F and Ebecryl 588), a monomerand photoinitiator. The ink-receptive and moisture-barrier coatings hadthe same compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

Example 4

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F 38 wt. % CN 301¹ 38wt. % TMPTA-N 20 wt. % Irgacure 184  4 wt. % Ink-Receptive Coating(Intercoat) Same composition as described in Example 1. Ink-ReceptiveCoating (Topcoat) Same composition as described in Example 1. PolymericCoating for Back Surface (Aqueous) Same composition as described inExample 1. ¹Polybutadiene dimethacrylate, Sartomer Company, Exton, PA19341.

In this Example 4, the radiation-curable coating contained tworadiation-curable oligomers (Laromer PE 44F and CN 301) along with amonomer and photoinitiator. The ink-receptive and polymeric coatings hadthe same compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

Example 5

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F 38 wt. % CN 302¹ 38wt. % TMPTA-N 20 wt. % Irgacure 184  4 wt. % Ink-Receptive Coating(Intercoat) Same composition as described in Example 1. Ink-ReceptiveCoating (Topcoat) Same composition as described in Example 1. PolymericCoating for Back Surface (Aqueous) Same composition as described inExample 1. ¹Polybutadiene diacrylate, Sartomer Company, Exton, PA 19341.

In this Example 5, the radiation-curable coating contained tworadiation-curable oligomers (Laromer PE 44F and CN 302) along with amonomer and photoinitiator. The ink-receptive and polymeric coatings hadthe same compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

Example 6

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Ebecryl 588 40 wt. % CN 301 40 wt. %TMPTA-N 15 wt. % Irgacure 184  5 wt. %Ink-Receptive Coating (Intercoat)Same composition as described in Example 1.Ink-Receptive Coating (Topcoat)Same composition as described in Example 1.Polymeric Coating for Back Surface (Aqueous)Same composition as described in Example 1.

In this Example 6, the radiation-curable coating contained tworadiation-curable oligomers (Ebecryl 588 and CN 301) along with amonomer and photoinitiator. The ink-receptive and polymeric coatings hadthe same compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

Example 7

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F 20 wt. % Ebecryl 58838 wt. % CN 301 20 wt. % TMPTA-N 17 wt. % Irgacure 184  5 wt. %Ink-Receptive Coating (Intercoat)Same composition as described in Example 1.Ink-Receptive Coating (Topcoat)Same composition as described in Example 1.Polymeric Coating for Back Surface (Aqueous)Same composition as described in Example 1.

In this Example 7, the radiation-curable coating contained threeradiation-curable oligomers (Laromer PE 44F, Ebecryl 588, and CN 301)along with a monomer and photoinitiator. The ink-receptive and polymericcoatings had the same compositions as described in Example 1. Theradiation-curable, ink-receptive, and polymeric coatings were applied toa 5.5 mil clay-coated paper (Centura Cover 60# paper) and treated in thesame manner as described in Example 1.

Example 8

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F 20 wt. % Ebecryl 58820 wt. % CN 302 38 wt. % TMPTA-N 17 wt. % Irgacure 184  5 wt. %Ink-Receptive Coating (Intercoat)Same composition as described in Example 1.Ink-Receptive Coating (Topcoat)Same composition as described in Example 1.Polymeric Coating for Back Surface (Aqueous)Same composition as described in Example 1.

In this Example 8, the radiation-curable coating contained threeradiation-curable oligomers (Laromer PE 44F, Ebecryl 588, and CN 302)along with a monomer and photoinitiator. The ink-receptive and polymericcoatings had the same compositions as described in Example 1. Theradiation-curable, ink-receptive, and polymeric coatings were applied toa 5.5 mil clay-coated paper (Centura Cover 60# paper) and treated in thesame manner as described in Example 1.

Example 9

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F 59 wt. % TMPTA-N 20wt. % Kronos 1072¹ 15 wt. % Esacure KTO-46² 3 wt. % Irgacure 184 1 wt. %Tinuvin 292³ 2 wt. % Ink-Receptive Coating (Intercoat) Water 73.5 wt. %Airvol 523S⁴ 4 wt. % PVP K-60 11 wt. % Sancure 815⁵ 11 wt. % BYK-380 0.5wt. % Ink-Receptive Coating (Topcoat) Water 65.6 wt. % Methocel E-15LV⁶5 wt. % Methocel K-3⁷ 1 wt. % PolyOX N80⁸ 1 wt. % Witcobond W-213 4 wt.% Dispal 23N4-20⁹ 23 wt. % BYK-380 0.4 wt. % Polymeric Coating for BackSurface (Aqueous) Rhoplex B-88¹⁰ 44.3 wt. % Haloflex 202-S¹¹ 44.3 wt. %Surfynol SE-F 0.9 wt. % Surfynol CT 171 0.2 wt. % DREW PLUS L-407 0.3wt. % Lanco PEW 1555 10 wt. % ¹Titanium dioxide, available from Kronos,Inc., Highstown, NJ 08520. ²Blend of trimethylbenzophenone, polymerichydroxy ketone, and trimethylbenzoyldiphenyl phosphine oxide, availablefrom Sartomer Company, Inc., Exton, PA 19341. ³Hindered amine lightstabilizer (HALS), available from Ciba Specialty Chemicals Corp.,Tarrytown, NY 10591. ⁴Polyvinyl alcohol, available from Air Products,Allentown, PA 18195. ⁵Polyurethane emulsion, available from BF GoodrichSpecialties Division, Cleveland, OH 44141. ⁶Hydroxypropylmethylcellulose, available from Dow Chemical Comp., Midland, MI 48642.⁷Hydroxypropyl methylcellulose, available from Dow Chemical Comp.,Midland, MI 48642. ⁸Polyethylene oxide, available from Union CarbideCorp., Danbury, CT 06817. ⁹Alumina sol, available from Vista ChemicalComp., Houston, TX 77079. ¹⁰Acrylic polymer emulsion, available fromRohm and Haas Comp., New Milford, CT 06776. ¹¹Vinyl acrylic terpolymeremulsion, available from NeoResins, Wilmington, MA 01887.

In this Example 9, the radiation-curable coating containedradiation-curable monomer (TMPTA-N) along with an oligomer (Laromer PE44F), titanium oxide pigment (Kronos 1072), two photoinitiators (EsacureKTO-46, Irgacure 184), dispersant agent, and light stabilizer (Tinuvin292). The radiation-curable coating was applied to a 5.5 mil clay-coatedpaper (Centura Cover 60# paper) and treated in the same manner asdescribed in Example 1.

The first ink-receptive coating (intercoat) was applied over theradiation-cured layer using a Meyer rod, and the coating was dried at225° F. The first ink-receptive layer comprised about 31% polyvinylalcohol, 38% polyvinyl pyrrolidone, 29% polyurethane, and 2% acrylicleveling agent by weight based on dry weight of the ink-receptive layer.The second ink-receptive coating (topcoat) was applied over theintercoat using a Meyer rod and dried at 225° F. The secondink-receptive layer comprised about 42% hydroxypropyl methylcellulose,7% polyethylene oxide, 8.5% polyurethane, 41% aluminum oxide, and 1.5%acrylic leveling agent by weight based on dry weight of theink-receptive layer.

The aqueous polymeric coating was applied to the backside of the paperusing a Meyer rod, and the coating was dried at 220° F. The polymericlayer comprised about 33% acrylic polymer, 47% vinyl acrylic terpolymer,18% low molecular weight polyethylene wax, 1.5% diol, and 0.5% modifiedpolysiloxane copolymer by weight based on dry weight of the polymericlayer.

Example 10

The following coating formulations were prepared.

UV Light Radiation-Curable Coating

Same composition as described in Example 3.

Ink-Receptive Coating (Intercoat)

Same composition as described in Example 9.

Ink-Receptive Coating (Topcoat)

Same composition as described in Example 9.

Polymeric Coating for Back Surface (UV light radiation-curable) LaromerPO 43F¹ 85 wt. % Gasil UV 70C² 10 wt. % Irgacure 184  5 wt. % ¹Polyetheracrylate oligomer, available from BASF Corp., Charlotte, NC 28273.²Silica dioxide, available from Crosfield, Joliet, IL 60435.

In this Example 10, the UV light-radiation curable coating had the samecomposition as described in Example 3. The ink-receptive coatings hadthe same compositions as described in Example 9. The radiation-curableand ink-receptive coatings were applied to a 5.5 mil clay-coated paper(Centura Cover 60# paper) and treated in the same manner as described inExample 1. The polymeric layer contained radiation-curable oligomer(Laromer PO 43F) and photoinitiator (Irgacure 184) along with silicadioxide (Gasil UV 70C).

EXAMPLE 11

The following coating formulations were prepared.

UV Light-Radiation Curable Coating Laromer 8981¹ 59 wt. % TMPTA-N 20 wt.% Ti-Pure R-960² 15 wt. % CGI 819 XF³ 1 wt. % Irgacure 184 3 wt. %Tinuvin 292 2 wt. % Ink-Receptive Coating Water 75.8 wt. % GelitaT-7838⁴ 11 wt. % Syntran HX31-65⁵ 13 wt. % Heloxy Modifier 48⁶ 0.2 wt. %Polymeric Coating for Back Surface (Aqueous) Same composition asdescribed in Example 9. ¹Polyester oligomer, available from BASF Corp.,Charlotte, NC 28273. ²Titanium dioxide, available from DuPont,Wilmington, DE 19880. ³Phenylbis(2,4,6-trimethyl benzoyl)-phosphineoxide, available from Ciba Specialty Chemicals Corp., Tarrytown, NY10591. ⁴Gelatin, available from Kind & Knox Gelatine, Inc., Sioux City,Iowa 51102. ⁵Acrylate copolymer, available from Interpolymer Corp.,Canton, MA 02021. ⁶Diglycidyl ether of dibromo neopentyl glycol,available from Shell Chemical Comp., Houston, TX 77252.

In this Example 11, the radiation-curable coating containedradiation-curable monomer (TMPTA-N) along with an oligomer (Laromer8981), titanium dioxide pigment (Ti-Pure R-960), two photoinitiators(CGI 819 XF, Irgacure 184), dispersant agent, and light stabilizer(Tinuvin 292). The radiation-curable coating was applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

The ink-receptive coating was applied over the radiation-cured layerusing a Meyer rod, and the coating was dried at 302° F. for 2 minutes.The ink-receptive layer comprised about 70% water-soluble gelatin, 29%acrylate copolymer, 1% diglycidyl ether of dibromo neopentyl glycol byweight based on dry weight of the ink-receptive layer.

The aqueous polymeric coating was applied to the backside of the paperand treated in the same manner as described in Example 9.

Example 12

The following coating formulations were prepared.

UV Light Radiation-Curable Coating

Same composition as described in Example 3.

Ink-Receptive Coating (Intercoat)

Same composition as described in Example 1.

Ink-Receptive Coating (Topcoat)

Same composition as described in Example 1.

Polymeric Coating for Back Surface

None

In this Example 12, the radiation-curable coating had the samecomposition as described in Example 3. The ink-receptive coatings hadthe same compositions as described in Example 1. The radiation-curableand ink-receptive coatings were applied to a 5.5 mil clay-coated paper(Centura Cover 60# paper) and treated in the same manner as described inExample 1. No polymeric coating was applied to the back surface of thepaper.

Example 13

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F 59 wt. % TMPTA-N 20wt. % Kronos 1072 15 wt. % Esacure KTO-46 3 wt. % Irgacure 184 1 wt. %Tinuvin 292 2 wt. % Ink-Receptive Coating Water 75 wt. % Gelita T-783811 wt. % Syntran HX31-65 13 wt. % Heloxy Modifier 48 0.2 wt. % PolymericCoating for Back Surface (Aqueous) Rhoplex B-88¹⁰ 44.3 wt. % Haloflex202-S¹¹ 44.3 wt. % Surfynol SE-F 0.9 wt. % Surfynol CT 171 0.2 wt. %DREW PLUS L-407 0.3 wt. % Lanco PEW 1555 10 wt. %

The radiation-curable coating was applied to a 5.5 mil clay-coated paper(Centura Cover 60# paper) and treated in the same manner as described inExample 1.

The ink-receptive coating was applied over the radiation-cured layerusing a Meyer rod, and the coating was dried at 302° F. (150° C.) for 2minutes. The aqueous polymeric coating was applied to the backside ofthe paper and treated in the same manner as described in Example 9.

The thermal stability of the radiation-cured layer on the papersubstrate was tested per the Test Methods described above. The test wasconducted at set temperatures in the range of 150° C. to 200° C., andthe coated surface was rated a “pass” at each temperature.

Example 14

The following coating formulations were prepared.

UV Light Radiation-Curable Coating

Same composition as described in Example 2.

Ink-Receptive Coating (Intercoat)

Same composition as described in Example 1.

Ink-Receptive Coating (Topcoat) Water 92.2 wt. % PVA KM118 3.5 wt. % PVPK-60 3 wt. % Syloid 72¹ 0.8 wt. % Citric acid 0.1 wt. % BYK-380 0.4 wt.% Polymeric Coating for Back Surface (Aqueous) Same composition asdescribed in Example 1. ¹Silica, available from Grace Davison,Baltimore, MD 21203.

In this Example 14, the radiation-curable coating had the samecomposition as described in Example 2. The first ink-receptive layer andpolymeric back coating had the same compositions as described in Example1.

The second ink-receptive layer comprised 59% polyvinyl alcohol, 23%polyvinyl pyrrolidone, 13% silica, 3% acrylic leveling agent, and 2%citric acid by weight based on dry weight of the ink-receptive layer.

The radiation-curable, ink-receptive, and polymeric back coatings wereapplied to a 5.5 mil clay-coated paper (Centura Cover 60# paper) andtreated in the same manner as described in Example 1.

Example 15

The following coating formulations were prepared.

UV Light Radiation-Curable Coating

Same composition as described in Example 2.

Ink-Receptive Coating (Intercoat)

Same composition as described in Example 1.

Ink-Receptive Coating (Topcoat) Water 92.6 wt. % PVA KM118 3 wt. % PVPK-60 2 wt. % Syloid 72 2 wt. % Citric acid 0.1 wt. % BYK-380 0.3 wt. %Polymeric Coating for Back Surface (Aqueous)Same composition as described in Example 1.

In this Example 15, the radiation-curable coating had the samecomposition as described in Example 2. The first ink-receptive layer andmoisture-barrier coatings had the same compositions as described inExample 1.

The second ink-receptive layer comprised 49% polyvinyl alcohol, 15%polyvinyl pyrrolidone, 32.5% silica, 2% acrylic leveling agent, and 1.5%citric acid by weight based on dry weight of the ink-receptive layer.

The radiation-curable, ink-receptive, and moisture-barrier coatings wereapplied to a 5.5 mil clay-coated paper (Centura Cover 60# paper) andtreated in the same manner as described in Example 1.

Example 16

In this Example 16, a continuous, in line process was used tomanufacture the ink-jet recording medium.

First, the UV-light radiation-curable coating described in Example 9 wasapplied to the front surface of a 5.5 mil clay-coated paper substrate(Centura Cover 60# paper available from Consolidated Papers Inc.) usingan offset gravure coater with a gravure roll (85 quad channeled roll) ata first coating station. The wet coating was cured by a Fusion UV lightcuring system (Model VP6/I600) (available from Fusion UV Systems, Inc.,Gaithersburg, Md. 20878) with two rows of 600 watts/cm H+-bulbs. The UVlamp power intensity was set at 100%. The line speed was greater than100 feet per minute (fpm). After progressing through the UV light curingstation, the web passed through a corona treatment station, wherein theradiation-cured layer was corona-treated using 2.5 kW of corona-treatingpower. After corona discharge treatment, the web progressed to a secondcoating station, where the inter-coat ink-receptive coating described inExample 9 was applied over the radiation-cured layer using a Meyer rod.The inter-coat was dried in an in-line dryer at 225° F. Then, the webprogressed to a third coating station, where the top coat ink-receptivecoating described in Example 9 was applied over the inter-coat layerusing a Meyer rod. The topcoat was dried in an in-line dryer at 225° F.Then, the running web passed over a turning bar. The back surface of therunning web was coated with the aqueous polymeric coating described inExample 9 in a fourth coating station. The aqueous back coating wasapplied using a Meyer rod, and the coating was dried at 220° F.

Comparative Example A

The following coating formulations were prepared.

UV Light Radiation-Curable Coating Laromer PE 44F 47.75 wt. % Laromer8765¹ 47.75 wt. % Irgacure 184  4.5 wt. % Ink-Receptive Coating(Intercoat) Same composition as described in Example 9. Ink-ReceptiveCoating (Topcoat) Same compostion as described in Example 9. PolymericCoating for Back Surface (Aqueous) Same composition as described inExample 1. ¹Epoxy polyacrylate (Oligomer), available from BASF Corp.,Charlotte, NC 28273

In this Comparative Example A, the radiation-curable coating containedtwo radiation-curable oligomers (Laromer PE 44F and Laromer 8965) andone photoinitiator (Irgacure 184). The ink-receptive coatings had thesame compositions as described in Example 9. The radiation-curablecoating and ink-receptive coatings were applied to a 5.5 mil clay-coatedpaper (Centura Cover 60# paper) and treated in the same manner asdescribed in Example 1.

Comparative Example B

The following coating formulations were prepared.

UV Light Radiation-Curable Coating

None

Ink-Receptive Coating

Same composition as described in Example 13.

Polymeric Coating for Back Surface

None (* JEN COAT 6 mil polycoated paper having a polyethylene coating onboth sides of the paper was used.)

The ink-receptive coating was applied to a JEN COAT 6 mil polycoatedwhite glossy paper (a polyethylene coated paper available from Jen-Coat,Inc. Westfield, Mass.) The ink-receptive coating was applied to thesurface of the paper using a Meyer rod, and the coating was dried at250° F. (121° C.) for 2 minutes.

The thermal stability of the radiation-cured layer on the papersubstrate was tested per the Test Methods described above. The test wasconducted at set temperatures in the range of 150° C. to 200° C., andthe coated surface was rated a “fail” at each temperature.

TABLE 1 Color WVT Surface Gloss Color Gamut Density Example (g/in²/24hrs.) (at 60° angle) Value (black color) Example 1 2.0 88 2609 2.58Example 2 2.0 89 2615 2.55 Example 3 2.0 89 2605 2.57 Example 4 2.0 882610 2.64 Example 5 2.0 89 2532 2.47 Example 6 2.0 88 2566 2.57 Example7 2.0 89 2620 2.63 Example 8 2.0 87 2609 2.53 Example 9 1.4 89 2601 2.78Example 4.7 87 2583 2.78 10 Example 1.4 97 2345 2.78 11 Example 3.8 892605 2.57 12 Example 1.4 97 2345 2.78 13 Example 2.0 41 2490 2.79 14Example 2.0  7 1605 1.87 15 Example 4.8 83 2454 2.45 16 Comp. Ex. 14.3 88 2601 2.78 A.

Referring to Table 1, in Comparative Example A, the UV lightradiation-curable coating contained two radiation-curable polyesteracrylate oligomers and a photoinitiator. The resultant mediumdemonstrated high surface gloss, but its water vapor transmission (WVT)rate was also high (14.3 grams/sq. in/24 hours).

However, as shown in Examples 1-16, it has been found that media havinglow water vapor transmission (WVT) rates and different surface glossvalues can be prepared using certain UV light radiation-curable,ink-receptive, and moisture-barrier coatings. Moreover, the media inExamples 1-16 provide ink-jet images having good color gamut and opticaldensity.

TABLE 2 (Water Fastness − Loss % of Color) Example Black Red GreenYellow Blue Magenta Cyan Ex. 13 35% 12%  4%  7%  4% 24%  4% Comp. B 54%45% 27% 12% 30% 31% 11%

Referring to Table 2, the ink-jet recording medium of Example 13demonstrated superior water-fastness versus the ink-jet recording mediumof Comparative Example B, although the same water-fast, ink-receptivecoating was applied to each of the substrates at the same coat weights.It is believed that the superior water-fastness of the medium in Example13 is due to it being treated at 302° F. (150° C.) for 2 minutes, whilethe medium in Comparative Example B was treated at 250° F. (121° C.) for2 minutes. As noted above, the JEN-COAT polycoated paper in ComparativeExample B failed the thermal stability test at 150° C.; thus, it had tobe heated at lower temperatures to achieve drying and other thermallyinduced changes. In Example 13, the greater thermal stability of theradiation-cured coating made it possible to process the ink-receptivelayer at higher temperatures and obtain superior water-fastnessproperties.

1. A continuous, in-line process for making an ink-jet recording medium,comprising the steps of: a) applying a radiation-curable coating to asurface of a substrate material, b) irradiating the radiation-curablecoating to form a freshly irradiated coating that undergoes a curingprocess, and c) applying an ink-receptive coating over the freshlyirradiated coating to form an ink-jet recording medium having a watervapor transmission rate of no greater than 12 grams/100 square inches/24hours and a surface gloss less than
 20. 2. A continuous, in-line processfor making an ink-jet recording medium, comprising the steps of: a)applying a radiation-curable coating to a surface of a substratematerial, b) irradiating the radiation-curable coating with ultravioletlight to form a freshly irradiated coating that undergoes a curingprocess, and c) applying an ink-receptive coating over the freshlyirradiated coating to form an ink-jet recording medium having a watervapor transmission rate of no greater than 12 grams/100 square inches/24hours and a surface gloss of at least
 70. 3. A continuous, in-lineprocess for making an ink-jet recording medium, comprising the steps of:a) applying a radiation-curable coating to a surface of a substratematerial, b) irradiating the radiation-curable coating to form a freshlyirradiated coating that undergoes a curing process, c) treating theirradiated coating with a corona discharge, and d) applying anink-receptive coating over the freshly irradiated coating to form anink-jet recording medium having a water vapor transmission rate of nogreater than 12 grams/100 square inches/24 hours and a surface gloss ofat least
 70. 4. A continuous, in-line process for making an ink-jetrecording medium, comprising the steps of: a) applying aradiation-curable coating to a surface of a substrate material, b)irradiating the radiation-curable coating to form a freshly irradiatedcoating that undergoes a curing process, c) applying a coatingcomprising adhesion promoters over the freshly irradiated coating and d)applying an ink-receptive coating over the coating comprising adhesionpromoters to form an ink-jet recording medium having a water vaportransmission rate of no greater than 12 grams/100 square inches/24 hoursand a surface gloss of at least
 70. 5. A continuous, in-line process formaking an ink-jet recording medium, comprising the steps of: a) applyinga radiation-curable coating to a surface of a substrate material,wherein the radiation-curable coating comprises a radiation-curableoligomer and photoinitiator, b) irradiating the radiation-curablecoating to form a freshly irradiated coating that undergoes a curingprocess, and c) applying an ink-receptive coating over the freshlyirradiated coating to form an ink-jet recording medium having a watervapor transmission rate of no greater than 12 grams/100 square inches/24hours and a surface gloss of at least
 70. 6. A continuous, in-lineprocess for making an ink-jet recording medium, comprising the steps of:a) applying a radiation-curable coating to a surface of a substratematerial, b) irradiating the radiation-curable coating to form a freshlyirradiated coating that undergoes a curing process, and c) applying anink-receptive coating over the freshly irradiated coating to form anink-jet recording medium having a water vapor transmission rate of nogreater than 12 grams/100 square inches/24 hours and a surface gloss ofat least 70, and further wherein the ink-receptive coating comprises atleast about 40% by weight water-soluble binder resin based on dry weightof the ink-receptive layer.
 7. The process of claim 6, wherein thewater-soluble binder resin is selected from the group consisting ofpolyvinyl alcohols; poly(vinyl pyrrolidone); poly(2-ethyl-2-oxazolinc);methylcellulose; poly(ethylene oxide); and copolymers and mixturesthereof.